package solution;

class TreeNode {
    int val;
    TreeNode left;
    TreeNode right;
    TreeNode() {}
    TreeNode(int val) { this.val = val; }
    TreeNode(int val, TreeNode left, TreeNode right) {
        this.val = val;
        this.left = left;
        this.right = right;
    }
}

class Solution {


    public TreeNode invertTree(TreeNode root) {
        invert(root);

        return root;
    }

    public void invert(TreeNode root) {
        if (null == root) {
            return;
        }

        TreeNode node = root.left;
        root.left = root.right;
        root.right = node;

        invert(root.left);
        invert(root.right);
    }
}